Along with the rapid development and wide application of wireless network system, and the popularization of cable TV network, many different solutions using the technology of transmission data signal in line with relevant wireless communication standard through existing coaxial cable of CATV network have been presented in recent years. On the other hand, signal transmission through existing CATV network will possess a large market share due to its high transmission efficiency and economic interests. However, the conventional wireless network uses 2.4 GHz or 5.8 GHz frequency is not suitable for signal transmission through the coaxial cable. The existing technical solution is modulating the wireless data signal, and then converting the modulated wireless data signal into a specific frequency range which is adapted for transmission through the coaxial cable.
For example, in the technology of WLAN using IEEE802.11 standard communication protocol, some signal combination apparatus, such as multiplexer for combining received IEEE802.11 wireless signal with the signal of CATV and transmitting signal through the coaxial cable, in order to use the coaxial cable of existing CATV network to transmit wireless signal from outside of the building to the subscribers in the building. The object of this solution is to extend wireless signal from external into internal of a building, so as to achieve a seamless coverage of the wireless signal and to ensure the quality of service.
Presently, there exist various types of applications for signal transmission through coaxial cable of CATV network. For example, UClink system is developed by Shenzhen Huawei based on ASIC protocol, of which the uplink and downlink frequency carriers are different frequency, instead of the IEEE802.11 standard protocol for data communication. Another existing technical solution adopts standard WIFI products, which transmits WIFI signal through the coaxial cable instead of antenna. A problem of this solution is that high frequency signal has only limited transmission distance, and the service providers of the network have to modify the original devices, e.g. band splits and transceivers etc. in order for proper use.
One Chinese patent application CN620132 discloses an integrated system for CATV network data transmission, which converts the IEEE802.11 signal down to 0-65 MHz signal for transmission through the coaxial cable network, characterized in that the standard IEEE802.11 signal of 2.4 GHz is converted to 0-65 MHz in a manner of OFDM (orthogonal frequency division multiplexing) with QAM (Quadrature Amplitude Modulation) or QPSK (Quadrature Phase Shift Keying) etc., and then transmitted through the coaxial cable network. Its frequency band range is partially overlapped with the CATV frequency, e.g. the CATV channel for Northern America which is about 54-550 MHz (except for 88 MHz to 108 MHz for the wireless frequency). Moreover, it is almost impossible to allocate more than one non-interference channel within such a narrow band width.
Another kind of known technical solution for transmitting signal through the coaxial cable converts the IEEE802.11 standard wireless signal from 2.4 GHz down to about 900-2000 MHz prior to transmitting the signal through the coaxial cable. For example, as illustrated in FIG. 1, an existing WIFI signal transceiver is provided for modulating the received WIFI signal, converting it into a suitable frequency band range, and then transmitting the converted signal through the coaxial cable. The signal transceiver comprises a processor unit 1a, an RF modulation/demodulation unit 2a, a tuner 4a and an RF frequency conversion unit 3a. The processor unit 1a has an interface connected in signal communication with an Ethernet network.
During the downlink transmission, the Ethernet data signal is received by the processor unit 1a through the interface from the Ethernet and transformed into WIFI standard baseband signal. Then the WIFI standard baseband signal is transmitted to the RF modulation/demodulation unit 2a. Conventionally, the 2.4 GHz WIFI signal range is divided into a number of smaller bands or ‘channels’. For example, in IEEE802.11b and IEEE802.11g standards, there are 13 channels for selection. The modulation/demodulation unit 2a modulates the WIFI standard baseband signal to frequency of 2.4 GHz or 5.8 GHz while a channel is selected by means of tuner 4a. And then the 2.4 GHz or 5.8 GHz signal is transmitted to the RF frequency conversion unit 3a, at which the 2.4 GHz or 5.8 GHz signal is down-converted into a range of 900 MHz to 2000 MHz to be transmitted through the coaxial cable. Such a frequency down-conversion is to avoid the specific frequency band being used by the CATV in order to prevent the signal of CATV from the interference. As shown in FIG. 2, when the client receives the signal with the down-converted frequency, at first, the down-converted frequency is up-converted into a signal of 2.4 GHz or 5.8 GHz by the RF frequency conversion unit 3a′. Then a channel of the 2.4 GHz or 5.8 GHz signal is selected and the signal is demodulated at unit 2a′ to a base band signal. The base band signal is converted by the processor unit 1a′ to an Ethernet data signal.
The uplink transmission is carried out in the opposite sequence to the down link one, and can be understood by referring to the description of the downlink and will not be further described here.
However, the conventional technology has a limitation on the bandwidth, so that it can not support multiple (e.g. five) non-overlapping channels. Therefore, it is desirable to develop an improved technical solution, which overcomes drawbacks and limitations of the prior arts.